[New evidence for the etiology of so-called radiation caries. Proof for directed radiogenic damage od the enamel-dentin junction].
OBJECTIVE
In spite of a great number of relevant studies the etiology of radiation induced caries still is discussed in controversy: The assumption of direct radiation induced lesions in the hard tissue is in contrast to an indirect pathogenesis mediated via radio-xerostomia.


METHODS
A systematic study is presented, comparing teeth with a manifest radiation caries (group 1, about 60 Gy, long interval to the extraction) and clinically caries free teeth (group 2, about 30 Gy, short interval) with tooth specimens after an experimental enoral (in situ) irradiation (60 Gy, group 3) and after in vitro irradiation (500 to 2,500 Gy, group 4). 60Co was the irradiation source. Sound teeth were used as a standard (group 5). For non destructive visualisation of subsurface histotomograms by confocal laser scanning microscopy (CLSM) teeth were either used as fresh sections or as Technovit embedded thin slices (sawing grinding technique).


RESULTS
Tooth samples from radiotherapy patients (cancer therapeutic doses, long interval before extraction; group 1) showed three characteristic changes: 1, rarefcation of the branching (ramification) of odontoblast processes near the junction, 2. dentine tubules end in front of the interface to the hard tissue and 3, in dentine the interface is characterised by an zone (about 10 microns wide) of low intensity of the remitted light.


CONCLUSIONS
The obliteration of the dentine tubules, preceded by a degeneration of the odontoblast processes, is obviously the result of a direct radiogenic cell damage with hampered vascularisation and metabolism particularly in the area of the terminations of the odontoblast processes. The deficit in metabolism combined with a latent damage of the parenchyma (hypo-remitting zone) is evidence for the functional symptoms (subsurface caries). The prerequisite for the micromorphological manifestation of this direct irradiation damage is a vital tooth and in consequence cannot be simulated in situ or in vivo.
Grötz
K A
KA
Klinik für Mund-, Kiefer- und Gesichtschirurgie, Klinikum der Johannes-Gutenberg-Universität Mainz.
Duschner
H
H
Kutzner
J
J
Thelen
M
M
Wagner
W
W
D003037:Cobalt Radioisotopes; D003731:Dental Caries / Q000209:etiology*; D003743:Dental Enamel / Q000528:radiation effects*; D003804:Dentin / Q000528:radiation effects*; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology*; D011878:Radiotherapy / Q000009:adverse effects*; D014070:Tooth / Q000528:radiation effects*; D014081:Tooth Extraction
D003037:Cobalt Radioisotopes
Neue Erkenntnisse zur Atiologie der sogenannten Strahlenkaries. Nachweis direkter radiogener Veränderungen an der Schmelz-Dentin-Grenze.